Dennise Jeannette Sullivan

Dennise Jeannette Sullivan’s is one of Utah’s oldest missing person cases. Dennise was 15 years old when she went missing under very violent circumstances. The general opinion is that she is presumed dead. This is the Case of the Month for December 2017.

Note: I have seen her name spelled as Dennise and as Denise. I use Dennise as that is the way she is profiled on NamUs.

Dennise (May 27, 1946 – missing July 4, 1961) is white with brown hair and brown eyes. According to NamUs (all used links in resources below) Dennise has a previously broken leg. It would be helpful when we compare unidentified Jane Does to know whether it was Dennise’s left or right leg that was previously broken. It could make all the difference in cases without any other way to identify found human remains. We do not have her dental chart but according to NamUs we do have DNA. Her NamUs profile also lists that she uses reading glasses.

The Case

In July 1961, Dennise Jeannette Sullivan was on vacation with her mother, Jeannette Sullivan (41), and her mother’s fiancé, Charles Boothroyd (55). They visited Dead Horse Point in Utah and were at a scenic spot near the Colorado River. There, Jeanette was shot in the back of her head with a .22 caliber rifle. Charles had two bullets in his face and hands (defensive wounds).

What Happened?

The killer pretended to have car trouble and asked them for a flashlight to look under the hood. Then he started his engine, turned towards the family, and demanded money while holding a rifle. Jeanette grabbed money bills from her purse, threw them on the ground, turned to walk away, and was shot in the back of her head. Charles was then shot in the face. While the killer dragged the bodies to the side of the road Dennise tried to get away in the family car. The killer followed and forced her off the road after about half a mile by a side-collision. He then forced her in his car and drove off. Boothroyd was left for dead, but he survived to tell police about the crime. Police searched by jeep, plane, and by boat but never found Dennise.

The Suspected Killer

According to the newspaper dated July 8, 1961 (link below) Abel B. Aragon shouted “Prove it!” to the FBI agents who stopped him. Then he took a .22 caliber pistol and shot himself in his temple. He died about two hours later.

Police believe that Aragon was the killer as his car bore the tell-tale signs of a collision. He was married with five children. Authorities think that Aragon was trying to get money to provide for his family. He was an unemployed coal miner. He had won the Navy Cross in 1944 as a marine for cleaning out a Japanese machine gun nest on Guam. From what I have seen online there do not seem to be other suspects.

Other Sources

I used NamUs’ database to search for a white teen alive around July 1961 last seen in Utah. I got no results.

The author Stephen Lacy wrote a book about this case. I have not read it but if you have, let me know what you think.

Contact Information

If you have any information that can help the authorities find Dennise please contact Lieutenant Kim Neal at (1)435-259-8115 at the Grand County Sheriff’s Office in Moab, Utah 84532.

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In the series “Case of the Month” I highlight old cold cases. These posts are not an in-depth analysis. Often more information is online or in newspaper archives. The goal of these posts is to get the cases back in the spotlights, to get people talking again, and if anything to make sure that we do not forget Dennise Jeannette Sullivan. Just because her case is cold does not mean that we can forget about her.

If you have any thoughts about this case I encourage you to post them on your social media platforms (Twitter, Facebook, Google Plus, etc.) Every time that we mention Dennise Jeannette Sullivan online we enhance her digital footprints. We must make sure that she keeps her web presence if we ever wish to find answers in her case. You can help by linking to or sharing this post.

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Thank you, Alice de Sturler